Great question!
There's a challenge in understanding how we have free will if Hashem, who's "all-knowing", knows what choices we're going to make. If Hashem knows exactly what we're going to do, and He knows that tomorrow morning you'll hit the snooze button twice, then it sounds like you have no choice, that it's inevitable!
The Rambam (Hilchos Teshuva 5:5) explains that in order to understand the paradox, we need to understand the idea of Hashem being outside of time (since He created time and space, He transcends them-- don't think about it too much, you'll get a headache). Since Hashem is beyond time, He can "see" your future choices because from His perspective, you've already made them.
Imagine that you're about to make a choice whether to have a second piece of cake. You're not sure what you're going to do. And imagine that I, observing you, could go into a time machine, go forward ten minutes into the future (it's now 4:15 and I go forward to 4:25). And I see that you're eating the cake. So I see what you ended up deciding.
Now I go back into the machine, and go back in time to 4:15, to see you still deliberating over the cake.
So I know what you're going to do. Does that take away your free will? Does my knowledge affect your choice? Of course not. The opposite is true. It's your choice that caused me to have the knowledge.
So Hashem knows your choices, but they're still, YOUR choices.
Deep idea but think about it. If we can wrap our heads for a minute around what it likes to be Hashem, we realize there's no contradiction here.
